In-situ remediation technologies for control or treatment of soils and groundwater are increasingly being investigated because they offer the potential for:

• significant cost reduction of clean-up by eliminating or minimizing exca­vation, transportation, and disposal of waste;

• reduction of health impacts on workers and the public by minimizing exposure to waste during excavation and processing;

• significant reduction in ecological impacts, and

• remediation of inaccessible sites, including deep sub-surfaces and in, under, and around buildings.

In-situ technologies can be subdivided into five major groups:

1. Containment technologies (e. g., bottom sealing, surface capping, polymer concrete barriers, cryogenic barriers, fluidized-bed zeolite system, plasma arc glass cup, slurry wall, soil/cement wall, vitrified barriers).

2. Solidification and stabilization (e. g., lime-fly ash Pozzolan system, organic binding, Pozzolan-Portland cement system, sorption, in-situ encapsulation, in-situ compaction).

3. Physical-chemical treatment (e. g., de-chlorination, electro-acoustics, electro-kinetics, neutralization, oxidation/reduction, precipitation/floc — culation, soil flushing, in-situ steam/air stripping, simultaneous injection, extraction and recharge, vacuum extraction).

4. Thermal treatment (e. g., radio frequency and electromagnetic heating, in-situ vitrification).

5. Biological treatment (e. g., biomass remediation, biodegradation).